• 分类：LinkedList

• 考察知识点：LinkedList

• 最优解时间复杂度：**O(n) **

61. Rotate List

Given a linked list, rotate the list to the right by k places, where k is non-negative.

Example 1:

Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:

Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL

代码：

方法:

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def rotateRight(self, head, k):
        """
        :type head: ListNode
        :type k: int
        :rtype: ListNode
        """
        if head==None or head.next==None:
            return head
        
        index=head
        length=1
        while index.next:
            index=index.next
            length+=1
            
        index.next=head
        
        i=0
        while(i<length-k%length):
            index=index.next
            head=head.next
            i+=1
        index.next=None
        return head

讨论：

1.一个首尾相连的方法，还是挺巧妙的

还是挺巧妙